JP7765285B2 - Ceramic products and decorative compositions - Google Patents

Description

The present invention relates to ceramic products and decorative compositions. More specifically, it relates to ceramic products having silver-colored decorative portions and decorative compositions for forming the silver-colored decorative portions.

Golden or silvery decorative parts are sometimes formed on the surfaces of ceramic products such as porcelain, glassware, and enamelware to give them an elegant or luxurious impression. Such decorative parts are formed, for example, by applying a composition containing a metal organic compound such as a metal resinate to the surface of the ceramic product and then firing it.

One example of a composition for forming the decorative portion described above is described in Patent Documents 1 and 2. Patent Documents 1 and 2 disclose a liquid gold for overglaze painting that contains gold (Au) as its main component and is used to form gold- or silver-colored decorative portions.

Japanese Unexamined Patent Publication No. 62-105990 Japanese Patent Application Publication No. 6-48779

It is preferable that ceramic products having decorative parts such as those described above give an elegant or luxurious impression when viewed visually. As a result of extensive research, the inventors have discovered that when only the gloss value, which indicates glossiness, is adjusted, the amount of reflected light changes depending on the viewing angle, causing the silver to appear cloudy (dull and whitish), and the luster (luster) of the silver decorative parts is not fully perceived.

The present invention was made in light of the above-mentioned circumstances, and its main object is to provide a ceramic product with a silver-colored decorative portion that, when visually inspected, has good luster and color development. Another object is to provide a decorative composition that can achieve such a silver-colored decorative portion.

To achieve the above object, the ceramic product disclosed herein has a silver decorative portion containing a precious metal component, the precious metal component being mainly composed of platinum, wherein the 8° gloss value of the silver decorative portion measured by the SCI method is 500 or more, and the value obtained by dividing the 8° gloss value by the lightness L ^* of the silver decorative portion measured by the SCE method (8° gloss value/lightness L ^* ) is 11 or more.
A ceramic product having such a configuration has a silver decorative part with sufficient gloss because the 8° gloss value of the decorative part is 500 or more. Furthermore, because the 8° gloss value/lightness L ^* is 11 or more, a silver decorative part that does not appear cloudy to the naked eye is realized. Therefore, with such a configuration, it is possible to provide a ceramic product having a silver decorative part that appears to be sufficiently glossy and colored to the naked eye.

In a preferred embodiment of the ceramic product disclosed herein, the silver decorative portion has an area ratio of the noble metal component of 37% or more based on observation with a field emission scanning electron microscope (FESEM).
According to this configuration, it is possible to provide a ceramic product having a silver decorative portion that has sufficient luster and color when visually inspected.

In the ceramic product disclosed herein, the precious metal component includes precious metal particles, and in an embodiment in which the area ratio of the precious metal component is 37% or more, the precious metal particles may have a cumulative 50% particle diameter ( _D50 ) of 5 nm or more in a number-based particle size distribution. In another preferred embodiment, the precious metal particles may have a cumulative 90% particle diameter ( _D90 ) of 20 nm or more in a number-based particle size distribution. In another preferred embodiment, the precious metal particles may have an arithmetic mean diameter of 35 nm or more.

In a preferred embodiment of the ceramic product disclosed herein, the silver decorative portion has a sheet resistance of 1×10 ⁴ Ω/□ or more.
With this configuration, a ceramic product is realized that has a silver decorative part that has sufficient luster and color when visually inspected, and that also has insulating properties that prevent sparks from occurring in a microwave oven.

To achieve the above-mentioned other object, a decorative composition is disclosed herein. The decorative composition disclosed herein is a decorative composition used for silver-coloring a ceramic substrate, and includes at least a precious metal element and a matrix-forming element. The precious metal element includes at least Pt, and the matrix-forming element includes a first element and a second element. The first element includes at least one element selected from the group consisting of Si and Bi, and the second element includes at least one element selected from the group consisting of Al, Zr, Ti, and rare earth elements. Here, the content of the precious metal element is 76 mol% to 95 mol%, and the content of the second element is 1.5 mol% or more, based on a molar ratio of the sum of the precious metal element and the matrix-forming element being 100 mol%.
According to this configuration, it is possible to form a silver decorative portion that has sufficient luster and color when visually inspected.

In a preferred embodiment of the ceramic product disclosed herein, the content of the second element is 1.5 mol % or more and 15 mol % or less when the total of the noble metal element and the matrix-forming element is 100 mol %.
This configuration makes it possible to suitably form a silver decorative portion that has a sufficient sense of luster and color development.

In a preferred embodiment of the ceramic product disclosed herein, the ceramic product has the following composition in molar ratio, with the total of the noble metal element and the matrix-forming element being 100 mol %:
Pt 60 mol% to 95 mol%,
a total of 0 mol % to 20 mol % of Au, Rh, Pd, and Ag;
a total of Si and Bi of 1 mol% to 16 mol%;
Al 0 mol% to 13 mol%,
Zr 0 mol% to 7 mol%,
Ti 0 mol% to 7 mol%,
Rare earth elements 0 mol% to 7 mol%
(However, when Al is 10 mol % or more, the rare earth element is 2 mol % or more.)
It has.
With this configuration, it is possible to form a silver decorative part that has sufficient luster and color to be visually perceived, and that has insulating properties that prevent sparks from occurring in a microwave oven.

1 is an FESEM observation image (20,000x) of the silver decorative portion according to Example 1. 10 is an FESEM observation image (20,000x) of the silver decorative portion according to Example 11. 1 is a binarized image of an FESEM observation image (20,000x magnification) of a silver decorative portion according to Example 1. 10 is a binarized image of an FESEM observation image (20,000x magnification) of the silver decorative portion of Example 11.

Preferred embodiments of the technology disclosed herein are described below. Matters necessary for implementation other than those specifically mentioned in this specification (such as methods for manufacturing ceramic substrates to be decorated) can be understood based on the technical content taught in this specification and the general technical common sense of those skilled in the art. The technology disclosed herein can be implemented based on the content disclosed in this specification and the general technical common sense of those skilled in the art. The notation "A to B" used in this specification to indicate a range means greater than A and less than B. Therefore, this includes cases where the range is greater than A and less than B.

1. Ceramic Product One embodiment of the ceramic product disclosed herein will now be described. The ceramic product disclosed herein includes a silver decorative portion containing a precious metal component. For example, the silver decorative portion may be provided on a substrate primarily composed of ceramic. Alternatively, for example, the substrate primarily composed of ceramic may include a coating layer primarily composed of an amorphous material (typically glass) and the silver decorative portion.

(1) Substrate The substrate is a molded body primarily composed of ceramics (e.g., a molded body having a ceramic content of 50% by mass or more). Ceramics constituting such a substrate include silica ( _SiO2 ), alumina ( _Al2O3 ), zirconia ( _ZrO2 ) _, magnesia (MgO), _titania ( _TiO2 ), ceria ( _CeO2 ), and yttria ( _Y2O3 ). The thickness, shape, hardness, and color of the substrate can be appropriately changed depending on the application of the ceramic product, and detailed description thereof is omitted as they do not limit the technology disclosed herein. Note that the chemical formulas shown in parentheses after the above substance names indicate representative compositions of the substances, and are not intended to limit the composition of actual ceramics to those chemical formulas.

(2) Coating Layer The coating layer is a layer mainly composed of an amorphous material (e.g., glass) (e.g., a layer containing 50% or more by mass of amorphous material). Such a coating layer can be formed on the surface of the substrate for purposes such as protecting the substrate. Note that the coating layer is not essential and can be omitted in other forms. Such a coating layer is formed, for example, by applying a glaze to the surface of the substrate and then firing it. Here, the glaze is a chemical agent containing metallic and semi-metallic elements that become oxides upon firing and form an amorphous matrix. This glaze may contain the same elements as those contained in the amorphous region of the silver decorative portion, or it may contain different elements.

The composition of the coating layer is not particularly limited as long as it does not significantly impair the effects of the technology disclosed herein, and conventionally known components that can be used to protect ceramic substrates can be appropriately selected. For example, the coating layer may contain Si, Al, Fe, Mg, Na, Zn, K, Ca, Sn, etc. These elements may form a matrix in the form of amorphous oxides. That is, the coating layer may form an amorphous matrix containing silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ ), magnesium oxide (MgO), potassium oxide (Na ₂ O), zinc oxide (ZnO), potassium oxide (K ₂ O), calcium oxide (CaO), tin oxide (SnO ₂ ), etc. The abundance ratio of each element in the coating layer does not limit the technology disclosed herein, and therefore a detailed description thereof will be omitted.

(3) Silver Decorative Portion The ceramic product disclosed herein has a silver decorative portion. The silver decorative portion can be formed on the surface of the substrate or the surface of the coating layer. The silver decorative portion of the ceramic product disclosed herein contains a precious metal component. The precious metal component can include precious metal particles. For example, the precious metal component may be composed of precious metal particles. Such a silver decorative portion has an 8° gloss value of 500 or more when measured using the SCI method, and a value obtained by dividing the 8° gloss value by the lightness L ^* when measured using the SCE method (8° gloss value/lightness L ^* ) of 11 or more. In other words, the silver decorative portion disclosed herein is a decorative portion that is glossy and exhibits a silver color with good color development.

The glossiness of the silver decorative portion can be evaluated by the 8° gloss value (hereinafter simply referred to as "8° gloss value") measured using the SCI method. Here, "8° gloss value" is a value indicating glossiness, and the higher the 8° gloss value, the glossier and more lustrous the silver decorative portion. The 8° gloss value can be measured using a spectrophotometer (such as the CM-700d or CM-600d manufactured by Konica Minolta Sensing, Inc.) designed to approximate a 60° gloss meter based on JIS Z 8741:1997. The SCI (Specular Components Include) method is a measurement method that includes specularly reflected light.

The color development of the silver decorative portion can be evaluated by the lightness L ^* (hereinafter simply referred to as "lightness L ^* ") measured using the SCE method. Lightness is a value indicating the degree of whiteness in the L ^* a ^* b ^* color system based on JIS Z 8781:2013, and the higher the lightness L ^* value, the whiter the color. Lightness L ^* can be measured using a spectrophotometer (e.g., the CM-700d or CM-600d manufactured by Konica Minolta Sensing Co., Ltd.) that complies with JIS Z 8722:2009. The SCE (Specular Components Exclude) method is a method that removes specular reflected light and measures only diffuse reflected light, and is also called the diffuse reflectance measurement method. With the SCE method, measured values vary depending on the surface condition even for the same color, and measurement results can be obtained that are close to those obtained when the color is recognized visually.

The silver decorative portion of a ceramic product can typically be produced by applying a decorative composition (described below) to the surface of a ceramic substrate (or coating layer) and firing it. During firing, silver decorative portions in which the precious metal particles are oversintered tend to have a low 8° gloss value and an excessively high lightness L ^* . This is presumed to be due to the following: For example, when a decorative composition with a high content of precious metal elements is applied to a ceramic substrate (e.g., porcelain) and fired, the precious metal particles tend to oversinter, causing aggregation and making it difficult for the precious metal components to disperse within the silver decorative portion. This reduces the color development in areas with low (or no) precious metal components, resulting in cloudiness and a corresponding decrease in gloss value (glossiness). Furthermore, when the precious metal particles are oversintered, unevenness with varying heights occurs on the surface of the silver decorative portion, which can also impair the gloss value (glossiness). Furthermore, in areas with low (or no) precious metal components, the color of the substrate (e.g., white) is more likely to show through. Therefore, lightness L ^* tends to be high. A silver decorative part with a low 8° gloss value and too high lightness L ^* does not have a sufficient silver luster to the naked eye and appears cloudy. Therefore, the inventors have conducted extensive research and found that by evaluating the silver decorative part based on both the 8° gloss value and the lightness L ^* , it is possible to achieve a silver decorative part that is free from cloudiness to the naked eye and has a good luster and color development.

Specifically, the silver decorative portion of the ceramic product disclosed herein has an 8° gloss value of 500 or more, and the value obtained by dividing the 8° gloss value by the lightness L ^* (8° gloss value/lightness L ^* ) is 11 or more. The 8° gloss value of the silver decorative portion is 500 or more, preferably 540 or more, or may be 600 or more, 675 or more, 710 or more, 780 or more, 830 or more, or even 900 or more. Furthermore, the 8° gloss value/lightness L ^* is 11 or more, preferably 11.5 or more, more preferably 20 or more, even more preferably 25.9 or more, or may be 33 or more, for example, 40 or more. Such a silver decorative portion has sufficient gloss, is not cloudy, and has good color development.

The lightness L ^* is not particularly limited as long as it is adjusted to satisfy the above value. For example, the lightness L ^* is preferably 10 or more, more preferably 20 or more, and may be 25 or more. If the lightness L ^* is too high, as described above, the result tends to be a whitish, cloudy silver color. From this viewpoint, the lightness L ^* is preferably 55 or less, more preferably 45 or less, and even more preferably 35 or less. For example, the lightness L ^* is preferably about 20 or more and 45 or less.

In order for the silver decorative part to exhibit a suitable silver color, it is preferable that the chromaticity a ^* and chromaticity b* in the L ^* a ^* b ^* color system based on JIS Z 8781:2013 be adjusted to values that are neither too high nor too low. Here, chromaticity a ^* and chromaticity b ^* indicate the color direction, with +a ^* indicating the red direction, -a ^* indicating the green direction, ⁺ b ^* indicating the yellow direction, and -b ^* indicating the blue direction. Measurement of such chromaticity a ^* and chromaticity b ^* can be performed using a spectrophotometer conforming to JIS Z 8722:2009.
Although not particularly limited, the chromaticity a ^* (hereinafter also simply referred to as "chromaticity a ^* ") when measured by the SCE method is, for example, preferably -10 or more and 10 or less, and more preferably -5 or more and 7 or less. Furthermore, the chromaticity b ^* (hereinafter also simply referred to as "chromaticity b ^* ") when measured by the SCE method is, for example, preferably -10 or more and 20 or less, more preferably -5 or more and 19 or less, and even more preferably -3 or more and 14 or less.

In order for the silver decorative portion to have suitable color development and luster, it is preferable that the precious metal particles are not over-sintered, as described above, and that the precious metal components have a certain area ratio when viewed from above. In one preferred embodiment, the silver decorative portion of the ceramic product disclosed herein has an area ratio of precious metal components of 37% or more based on observation with a field emission scanning electron microscope (FESEM). The area ratio of precious metal components based on FESEM observation may be 39% or more, 43% or more, or 50% or more. From the perspective of ensuring the insulation properties described below, the upper limit of the area ratio of precious metal components based on FESEM observation is preferably 90% or less, and may be 85% or less, for example.

Here, the "area ratio (%) of precious metal components based on FESEM observation" in this specification can be determined as follows. First, each sample is fixed horizontally to the sample stage so that the surface of the silver decorative portion applied to the substrate is facing up, and an osmium plasma coater (e.g., OPC80N manufactured by Japan Laser Electronics Co., Ltd.) is used to coat the surface and prepare a measurement sample coated with osmium. The osmium coating conditions are, for example, a discharge voltage of 1.2 kV, a vacuum of 6 to 8 Pa, and a coating time of 10 seconds. Next, using a field emission scanning electron microscope (e.g., SU8230 manufactured by Hitachi High-Technologies Corporation), multiple FESEM observation images (e.g., 3 to 20 images) of the surface of the silver decorative portion are randomly obtained. At this time, an area free of scratches, impurities, or other obstacles to image analysis is selected to obtain the image. The conditions for acquiring the FESEM observation image may be set to, for example, an acceleration voltage of 10.0 kV and an emission current of 10±0.5 μA. The magnification of the field of view of the FESEM observation image may be adjusted appropriately so that the number of countable particles in one field of view is 1,000 to 10,000, for example, 1,000 to 100,000 times.
Next, the acquired FESEM observation images are binarized using the well-known image processing software Image J (ver. 1.53e) so that the acquired multiple FESEM observation images are colored black for the precious metal components and white for the other components (e.g., matrix-forming components). In the binarization process, the brightness threshold for distinguishing between the regions of the precious metal components and the regions of the other components can be a value determined by the automatic settings of Image J. The acquired FESEM observation images are then binarized by defining high-brightness regions (i.e., regions where the brightness threshold is equal to or greater than the value determined by the automatic settings) as regions of the precious metal components and low-brightness regions (i.e., regions where the brightness threshold is less than the value determined by the automatic settings) as regions of the other components. The threshold determined by the automatic settings varies depending on the contrast and brightness of the acquired FESEM images, so is not particularly limited. However, for FESEM images acquired by the above method, a brightness value of 50 to 150 is generally set as the threshold. For each of the acquired multiple FESEM observation images, the area of the black portion relative to the area of the entire FESEM observation image is calculated, and the "area ratio (%) of the precious metal component based on FESEM observation" in this specification can be determined by calculating the average of these values.

The precious metal component of the silver decorative portion of the ceramic product disclosed herein may contain precious metal particles. It is generally known that in decorative films formed on ceramic substrates, if the particle diameter of the precious metal particles contained in the decorative film becomes too small, the silver coloring property decreases, resulting in a coloring due to surface plasmon resonance of the precious metal particles (for example, if the precious metal particles are Pt particles, the coloring becomes more brownish). Therefore, even if the area ratio of the precious metal component based on FESEM observation is 37% or more, if the particle diameter of the precious metal particles that can constitute the precious metal component becomes excessively small (for example, if the _D50 in the number-based particle size distribution of the precious metal particles is less than 5 nm), the silver coloring property may be visually reduced. In other words, in order to achieve a silver decorative portion with better coloring and gloss, it is preferable that the particle diameter of the precious metal particles is not excessively small.

In a preferred embodiment, the precious metal particles contained in the precious metal component of the silver decorative portion of the ceramic product have a cumulative 50% particle diameter ( _D50 ) of 5 nm or more in the number-based particle size distribution. _D50 is, for example, more preferably 8 nm or more, even more preferably 11 nm or more, and may even be 30 nm or more. The upper limit of _D50 may be adjusted to satisfy the above-mentioned area ratio of the precious metal component, and is, for example, preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. This allows for the realization of a ceramic product having a silver decorative portion with good silver color development.
In this specification, the "cumulative 50% particle diameter (D ₅₀ ) in the number-based particle size distribution" can be determined as follows. First, the acquired FESEM observation image is subjected to binarization processing using Image J as described above. Next, the area of the precious metal particles is measured using the "Analyze particles" function of Image J (ver. 1.53e). The measurement conditions at this time should be set to 0-infinity for both size and circularity. The magnification of the FESEM image should be set so that the sintered precious metal particles can be accurately counted. For example, the magnification of the FESEM image should be adjusted so that the number of particles counted in one field of view is 1,000 or more. At this time, particles present on the edge of the image are also set as targets to be counted. On the other hand, if the number of particles counted in one field of view is too large, the outlines of each precious metal particle may become blurred, making it impossible to accurately measure the area. Therefore, it is advisable to adjust the magnification of the FESEM image so that the number of particles counted in one field of view is not more than 10000. Then, based on the area of the precious metal particles, the circle-equivalent diameter of each precious metal particle can be calculated using the following formula (1).
D=2×(π/S) ^0.5 (1)
Here, D in formula (1) is the "circle equivalent diameter (nm)" and S is the "area (nm ² ) of the noble metal particle obtained by image analysis processing."
Then, a number-based particle size distribution is created by arranging the calculated circle-equivalent diameters of at least 1,000 particles in order of particle size, and the particle diameter corresponding to a cumulative frequency of 50 number % in the particle size distribution is defined as the "cumulative 50% particle diameter (D ₅₀ ) in the number-based particle size distribution" in this specification.

In a preferred embodiment, the precious metal particles have a cumulative 90% particle diameter ( _D90 ) of 20 nm or more in the number-based particle size distribution. _D90 is, for example, more preferably 35 nm or more, even more preferably 45 nm or more, and may be 50 nm or more. The upper limit of _D90 may be adjusted to satisfy the area ratio of the precious metal component, and may be, for example, 800 nm or less, preferably 650 nm or less, and more preferably 500 nm or less. This allows for the realization of a ceramic product having a silver decorative portion with good silver color development.
The "cumulative 90% particle diameter ( _D90 ) in the number-based particle size distribution" in this specification can be determined as follows. First, the circle-equivalent diameter is calculated as described above in the acquired FESEM observation image. Then, a number-based particle size distribution is created by arranging the calculated circle-equivalent diameters of at least 1,000 particles in order of particle diameter, and the particle diameter corresponding to a cumulative frequency of 90 number % in this particle size distribution is defined as the "cumulative 90% particle diameter ( _D90 ) in the number-based particle size distribution" in this specification.

In a preferred embodiment, the arithmetic mean diameter of the precious metal particles is 35 nm or more. The arithmetic mean diameter of the precious metal particles is, for example, more preferably 40 nm or more, even more preferably 50 nm or more, and may be 70 nm or more. On the other hand, the upper limit of the arithmetic mean diameter of the precious metal particles is not particularly limited, but is, for example, preferably 1250 nm or less, more preferably 500 nm or less, even more preferably 330 nm or less, and may be, for example, 280 nm or less. This allows for the realization of a ceramic product having a silver decorative portion with good silver color development.
The "arithmetic mean diameter of noble metal particles" in this specification can be determined as follows. First, the circle-equivalent diameter is calculated as described above in the acquired FESEM observation image. Then, the circle-equivalent diameters are calculated for at least 1,000 particles, and the average of the calculated circle-equivalent diameters is calculated, thereby determining the "arithmetic mean diameter of noble metal particles."

In a preferred embodiment, the silver decorative portion of the ceramic product disclosed herein is insulating. In this specification, "insulating" means that the sheet resistance is 1 x 10 ⁴ Ω/□ or more. A silver decorative portion having such a sheet resistance is insulating and does not spark when heated in a microwave oven. Such a sheet resistance can be measured, for example, by the four-probe method.
If the precious metal particles are over-sintered, a region where the precious metal particles are densely present may be formed. This may cause the silver decorative portion of the ceramic product to have electrical conductivity. Therefore, from the viewpoint of ensuring insulation, it is preferable to suppress the over-sintering of the precious metal particles.

The precious metal component of the silver decorative portion of the ceramic product disclosed herein is primarily composed of platinum. In this specification, "the precious metal component is primarily composed of platinum" means that the Pt content (mol%) is the highest when the total amount of precious metal elements contained in the precious metal component is 100 mol%. Preferably, the Pt content is 70 mol% or more when the total amount of precious metal elements contained in the precious metal component is 100 mol%. The Pt content may be 75 mol% or more, 79 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more, for example, 100 mol%. The Pt content is preferably 70 mol% or more to 100 mol%, more preferably 70 mol% or more to 99.5 mol%, and even more preferably 78 mol% or more to 99 mol%. This allows for a silver decorative portion with good color development. The content of each element in the silver decorative portion can be measured, for example, by elemental analysis using a general scanning electron microscope (SEM)-energy dispersive X-ray spectroscopy (EDX).
The precious metal components contained in the silver decorative portion of the ceramic product disclosed herein may be composed of the precious metal elements contained in the decorative composition described below. In other words, the proportion of the precious metal elements in the silver decorative portion may roughly reflect the proportion of the precious metal elements in the decorative composition. Here, "precious metal elements" typically include platinum (Pt), gold (Au), rhodium (Rh), and silver (Ag). They may also include iridium (Ir), palladium (Pd), ruthenium (Ru), and osmium (Os).

The silver decorative portion may or may not contain Au, Rh, Pd, Ir, and Ag as the precious metal elements contained in the precious metal component. When the above precious metal elements are contained in the silver decorative portion, for example, the total of Au, Rh, Pd, Ir, and Ag is preferably 30 mol% or less, and more preferably 25 mol% or less. When Au is contained in the silver decorative portion, the content of Au may be 0.1 mol% to 25 mol%, or 3 mol% to 20 mol%, when the total of the precious metal elements contained in the precious metal component is 100 mol%. When Rh is contained in the silver decorative portion, the content of Rh may be 0.1 mol% to 7 mol%, or 0.5 mol% to 2 mol%, or 0.5 mol% to 1.5 mol%. When Ir is contained in the silver decorative portion, the Ir content may be 0.1 mol% to 7 mol% or 0.5 mol% to 2 mol% or 0.5 mol% to 1.5 mol%. When Pd is contained in the silver decorative portion, the Pd content may be 0.1 mol% to 10 mol% or 1 mol% to 7 mol%. When Ag is contained in the silver decorative portion, the Ag content may be 0.1 mol% to 12 mol% or 1 mol% to 10 mol%.

The silver decorative portion is typically formed as a film on the surface of the substrate (or coating layer) of the ceramic product. There are no particular limitations on the average thickness of the silver decorative portion, but it is preferably 20 nm to 300 nm, and more preferably 50 nm to 150 nm. A silver decorative portion with such an average thickness will achieve a good silver color without the color of the ceramic substrate showing through. The average thickness of such a silver decorative portion can be adjusted as appropriate, for example, by the application method.

2. Decorative Composition One embodiment of the decorative composition disclosed herein is described below. By applying this decorative composition to the surface of a substrate (or coating layer) of a ceramic product and firing it, a ceramic product can be produced with a silver-colored decorative portion exhibiting excellent gloss and color development, as described above. The decorative composition disclosed herein contains at least a precious metal element and a matrix-forming element. The precious metal element includes at least platinum (Pt). The matrix-forming element includes at least a first element and a second element. Here, the first element includes at least one element selected from the group consisting of silicon (Si) and bismuth (Bi). The second element includes at least one element selected from the group consisting of aluminum (Al), zirconium (Zr), titanium (Ti), and rare earth elements. The various components that may be contained in the decorative composition disclosed herein are described in detail below.

(1) Precious Metal Elements Precious metal elements are components that contribute to the coloring of the fired decorative composition (i.e., the silver decorative portion). As described above, the decorative composition disclosed herein contains at least Pt as a precious metal component. Specific examples of precious metal elements that may be included in addition to Pt include gold (Au), rhodium (Rh), silver (Ag), iridium (Ir), palladium (Pd), ruthenium (Ru), and osmium (Os). The precious metal elements may be contained in the decorative composition in the form of, for example, a metal resinate (an organic metal compound). The state of the precious metal elements in the decorative composition is not limited to the metal resinate described above, but may also be a complex, a polymer, or metal particles.

The content of the precious metal element in the decorative composition disclosed herein is at least 76 mol% or more, where the sum of the precious metal element and matrix-forming element contained in the decorative composition is 100 mol%. The content of the precious metal element is preferably 79 mol% or more, more preferably 82 mol% or more, and may be 85 mol% or more, 90 mol% or more, or even 94 mol% or more. Furthermore, because the decorative composition disclosed herein contains a matrix-forming element, the content of the precious metal element is 97 mol% or less, may be 96 mol% or less, and preferably 95 mol% or less. By including a predetermined proportion of the second element described below, the decorative composition disclosed herein can suppress over-sintering of the precious metal particles, even in compositions with a high content of the precious metal element, thereby producing a silver decorative portion with a clear, well-colored silver finish. In the following description, unless otherwise specified, the "content of a specific element in a decorative composition" refers to the content (mol %) of the specific element when the total of the precious metal elements and matrix-forming elements contained in the decorative composition is taken as 100 mol %.

Platinum (Pt) is the component that imparts the lustrous silver-like hue to the silver decorative portion. Pt is the major constituent element among the precious metal elements contained in the decorative composition (i.e., the element with the highest content among the precious metal elements in the decorative composition). Pt is included in the decorative composition, for example, as a constituent element of Pt resinate. Pt resinate has the property of forming Pt particles with larger particle diameters than other precious metal elements upon firing. As a result, Pt particles are less likely to sinter than other precious metal elements. This makes it easier for Pt particles to be separated from each other in the decorative portion of the decorative composition, thereby suppressing electrical conductivity. As a result, the decorative composition disclosed herein can achieve a silver decorative portion that has favorable insulating properties and does not spark when heated in a microwave oven, even when the silver decorative portion contains a low content of components that reduce electrical conductivity (e.g., matrix-forming components such as Si and Bi).

Among the precious metal elements mentioned above, Pt is preferred because it exhibits particularly excellent color development, making it relatively easy to form silver decorative parts that give an elegant or luxurious impression. The Pt content in the decorative composition is preferably 60 mol% or more, more preferably 66 mol% or more, and may be 70 mol% or more, 80 mol% or more, or even 90 mol% or more. On the other hand, if the Pt content in the decorative composition is too high, the number of Pt particles in the silver decorative part will be excessively large. As mentioned above, Pt particles tend to have a large particle size, which can cause unevenness with differences in height on the surface of the silver decorative part and impair gloss. Therefore, the Pt content in the decorative composition is suitably 97 mol% or less, may be 96 mol% or less, and preferably 95 mol% or less.

Gold (Au), rhodium (Rh), palladium (Pd), iridium (Ir), and silver (Ag) are components that adjust the silver hue in the fired body (i.e., the silver decorative portion) of the decorative composition. The decorative composition disclosed herein may or may not contain Au, Rh, Pd, Ir, and Ag. When Au is included, the content of Au in the decorative composition is preferably 1 mol% to 20 mol%, and more preferably 3 mol% to 17 mol%. When Rh is included, the content of Rh in the decorative composition is preferably 0.1 mol% to 5 mol%, and more preferably 0.8 mol% to 3 mol%. When Pd is included, the content of Pd in the decorative composition is preferably 0.1 mol% to 10 mol%, and more preferably 1 mol% to 8 mol%. When Ir is contained, the Ir content in the decorative composition is preferably 0.1 mol% to 5 mol%, and more preferably 0.8 mol% to 3 mol%. When Ag is contained, the Ag content in the decorative composition is preferably 0.1 mol% to 10 mol%, and more preferably 1 mol% to 8 mol%.

(2) Matrix-forming elements In this specification, the term "matrix-forming elements" refers to metal elements and metalloid elements that can form an amorphous matrix in the oxide state in the fired body (silver decorative part) of the decorative composition. Furthermore, the term "amorphous matrix" refers to a structure in which amorphous oxides (oxides with an amorphous structure) of specific metal elements and metalloid elements form a skeleton, and various metal elements (or metalloid elements) exist within the skeleton as oxides or in the form of cations. An example of a material with an amorphous matrix (amorphous material) is glass. Examples of such matrix-forming elements include Si, Bi, Zr, Ti, Al, Ni, Cr, Sm, Y, La, Ce, Pr, Nd, Sm, Dy, Sn, Zn, Be, Mg, Ca, Sr, Ba, Li, Na, K, Rb, B, V, Fe, Cu, P, Sc, Pm, Eu, Gd, Tb, Ho, Er, Tm, Yb, Lu, In, and Co. Among the above-mentioned noble metal elements, there are elements (e.g., Ag) that can become amorphous oxides during firing and constitute part of the amorphous matrix. However, for convenience, the elements listed in (1) noble metal elements above are not considered to be matrix-forming elements in this specification.
As with the noble metal elements, the form of the matrix-forming components in the decorative composition is not particularly limited, and may take the form of metal resinates (organic metal compounds), complexes, polymers, fine particles (glass frit), etc.

The decorative composition disclosed herein contains a matrix-forming element. The matrix-forming element includes at least one first element selected from the group consisting of silicon (Si) and bismuth (Bi), and at least one second element selected from the group consisting of aluminum (Al), zirconium (Zr), titanium (Ti), and rare earth elements. The content of the matrix-forming element in the decorative composition is preferably 3 mol% or more, more preferably 4 mol% or more, and even more preferably 5 mol% or more. Considering the balance with the above-mentioned precious metal elements, the content of the matrix-forming element in the decorative composition is preferably 24 mol% or less, more preferably 21 mol% or less, and even more preferably 18 mol% or less.

(a) First Element As described above, the decorative composition disclosed herein contains silicon (Si) and/or bismuth (Bi) as the first matrix-forming element. Si and Bi are components that form the framework of the amorphous matrix in the form of silicon oxide (SiO ₂ ) or bismuth oxide (Bi ₂ O ₃ ) after firing. The content of the first element (i.e., the total content of Si and Bi) in the decorative composition is preferably 1 mol % or more, more preferably 1.4 mol % or more, and may be 3 mol % or more, and even more preferably 10 mol % or more. On the other hand, if the content of the first element is too high, the luster of the silver decorative portion may be lost. For this reason, the content of the first element in the decorative composition is preferably 16 mol % or less, and may be 13 mol % or less.

As mentioned above, Si is a component that forms the framework of the amorphous matrix and can improve the strength of the silver decorative portion. When Si is included as the first element, the Si content in the decorative composition is preferably 1 mol% to 16 mol%, more preferably 3 mol% to 14 mol%, and even more preferably 5 mol% to 11 mol%. Furthermore, Bi is a component that forms the framework of the amorphous matrix and has the effect of softening the amorphous matrix (glass), thereby improving adhesion to the substrate. When Bi is included as the first element, the Bi content in the decorative composition is preferably 0.1 mol% to 5 mol%, more preferably 0.3 mol% to 3 mol%, and even more preferably 1 mol% to 2 mol%.

(b) Second Element As described above, the decorative composition disclosed herein contains at least one element selected from the group consisting of aluminum (Al), zirconium (Zr), titanium (Ti), and rare earth elements as the second matrix-forming element. By incorporating the second element in a predetermined content in the decorative composition, a silver decorative part with a clear, silver color and good color development can be achieved. While not intending to limit the technology disclosed herein, the reason for this effect is presumed to be as follows. As described above, if the decorative composition contains a high content of precious metal elements, the precious metal particles may over-sinter during firing, reducing the color development of the silver decorative part. It is presumed that the second element (Al, Zr, Ti, rare earth element) can prevent such over-sintering of the precious metal particles. Therefore, even if the decorative composition contains a high content of precious metal elements, by incorporating a predetermined amount of the second element, a silver decorative part with a clear, silver color and good color development can be achieved.

If the content of the second element in the decorative composition is too low, the effect of preventing the above-mentioned over-sintering of the precious metal particles will not be fully achieved. Therefore, the content of the second element in the decorative composition is at least 1.5 mol% or more. The content of the second element in the decorative composition is 1.5 mol% or more, preferably 2 mol% or more, and may be 4 mol% or more, or 5 mol% or more. On the other hand, if the content of the second element in the decorative composition is too high, the content of the precious metal element will decrease, which may result in a decrease in color development. From this perspective, the content of the second element in the decorative composition is preferably 20 mol% or less, more preferably 15 mol% or less, and may be 10 mol% or less, or may be 9 mol% or less. By adjusting the content of the second element in the decorative composition within the above range, it is possible to preferably achieve a silver decorative portion having the above-mentioned characteristics.

The rare earth element can be selected without limitation from scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Based on extensive research conducted by the inventors, among the rare earth elements listed above, Y, Sm, Pr, Nd, La, Ce, Dy, and Ho are preferred. Furthermore, Y and Sm are particularly preferred because their inclusion as secondary elements in the decorative composition can fully exert the effects described above.

As mentioned above, aluminum (Al) is a component that prevents the precious metal particles from over-sintering and improves the color development of the silver decorative portion. When Al is included as the second element, the Al content in the decorative composition is preferably 1.5 mol% or more, more preferably 2.5 mol% or more, and even more preferably 5 mol% or more. This results in a silver decorative portion that is free of cloudiness and has good color development. The Al content in the decorative composition is 16 mol% or less, preferably 13 mol% or less, and more preferably 10 mol% or less.

While an appropriate amount of Al can prevent the precious metal particles from over-sintering, experiments have confirmed that too much Al can cause the silver decorative portion to become conductive. Therefore, in one preferred embodiment, when the second element contains 10 mol% or more of Al, it is advisable to also contain 2 mol% or more of the rare earth elements listed above. This makes it possible to achieve a silver decorative portion with good color development and sufficient insulation properties.

In a preferred embodiment, the aluminum component in the decorative composition is preferably in the form of an organometallic compound or oxide fine particles. Examples of organometallic compounds include metal resinates and metal chelate compounds. Metal resinates contain aluminum as a constituent element and an organic compound, as described below. More specifically, the decorative composition may contain aluminum resinates or other such compounds. Metal chelate compounds are chelate compounds containing aluminum as a constituent element, such as aluminum ethylacetoacetate diisopropylate, aluminum tris(ethylacetoacetate), aluminum alkylacetoacetate diisopropylate, aluminum monoacetylacetonate bis(ethylacetoacetate), and aluminum tris(acetylacetonate). Furthermore, alumina (Al ₂ O ₃ ) fine particles are preferably used as the oxide fine particles. The oxide fine particles preferably have an average particle diameter of approximately 25 nm to 100 nm. In this specification, the "average particle size of oxide fine particles" refers to the particle size (D ₅₀ ) at which the cumulative volume is 50% in the volume-based particle size distribution based on the laser diffraction/scattering method.

When zirconium (Zr), titanium (Ti) and rare earth elements are contained in the decorative composition in appropriate amounts, they prevent the precious metal particles from over-sintering as described above and improve the color development of the silver decorative parts.
When Zr is included as the second element, the Zr content in the decorative composition is preferably 0.1 mol% to 7 mol%, and more preferably 1 mol% to 6.5 mol%. When Ti is included as the second element, the Ti content in the decorative composition is preferably 0.1 mol% to 7 mol%, and more preferably 1 mol% to 6.5 mol%. When a rare earth element is included as the second element, the rare earth element content in the decorative composition is preferably 0.1 mol% to 7 mol%, and more preferably 0.7 mol% to 7 mol%, and even more preferably 2 mol% to 6.5 mol%.

(c) Other Elements The decorative composition disclosed herein may contain metal elements or metalloid elements other than those described above as matrix-forming elements, provided that the effects of the technology disclosed herein are not impaired. Examples of such other elements include Sn, Zn, Be, Mg, Ca, Sr, Ba, Li, Na, K, Rb, B, V, Fe, Cu, and P. The decorative composition does not necessarily contain other elements. When other elements are contained in the decorative composition, the content of the other elements in the decorative composition may be 3 mol % or less, or even 2.5 mol % or less.

(3) Other Components The above describes the precious metal elements and matrix-forming elements of the decorative composition disclosed herein. In addition to the above-mentioned components, the decorative composition disclosed herein preferably contains various other components in consideration of the adhesion to the surface of the ceramic product (more specifically, the substrate or coating layer) and the formability of the decorative portion. Below, we will explain other components that may be included in the decorative composition disclosed herein. However, the other components described below can be any conventionally known components that can be used in decorative compositions, without any particular restrictions, as long as they do not significantly interfere with the effects of the technology disclosed herein. In other words, the decorative composition disclosed herein can be modified in components other than the above-mentioned essential elements as appropriate depending on its intended use.

First, as mentioned above, the decorative composition disclosed herein may contain both the precious metal element and the matrix-forming element in the form of a metal resinate. In this case, the decorative composition contains an organic compound for forming the metal resinate. Any conventionally known resin material that can be used to produce a metal resinate can be used as the organic compound, without particular limitation. Examples of such resin materials include carboxylic acids with a high carbon number (e.g., 8 or more carbon atoms) such as octylic acid (2-ethylhexanoic acid), abietic acid, naphthenic acid, stearic acid, oleic acid, linolenic acid, and neodecanoic acid; sulfonic acids; resin acids contained in rosin; resin sulfide balsam containing essential oil components such as turpentine oil and lavender oil; alkyl mercaptides (alkylthiolates); aryl mercaptides (arylthiolates); mercaptocarboxylic acid esters; and alkoxides.

In addition, decorative compositions containing both precious metal elements and matrix-forming elements in the form of metal resinates preferably use an organic solvent that disperses or dissolves the metal resinates. Such organic solvents can be any of those traditionally used in resinate pastes or liquid gold solutions, with no particular restrictions. Examples of organic solvents include 1,4-dioxane, 1,8-cineole, 2-pyrrolidone, 2-phenylethanol, N-methyl-2-pyrrolidone, p-tolualdehyde, benzyl benzoate, butyl benzoate, eugenol, caprolactone, geraniol, methyl salicylate, cyclohexanone, cyclohexanol, cyclopentyl methyl ether, citronellal, di(2-chloroethyl)ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, dihydrocarvone, dibromomethane, dimethyl sulfoxide, dimethylformamide, nitrobenzene, pyrrolidone, propylene glycol monophenyl ether, pulegone, benzyl acetate, benzyl alcohol, benzaldehyde, turpentine oil, and lavender oil. These organic solvents may be used alone or in combination. Metal resinates are commercially available as resinate pastes, for example, and such resinate pastes may be used as is.

The weight ratio of the solvent that can be contained in the decorative composition is not particularly limited, as the preferred range varies depending on the application method of the decorative composition, and can be adjusted as appropriate. For example, the weight ratio of the solvent should be approximately 10 wt% to 50 wt% when the entire decorative composition is taken as 100 wt%. As an example, when applying by inkjet, the weight ratio of the solvent should preferably be, for example, 10 wt% to 50 wt% when the entire decorative composition is taken as 100 wt%. As another example, when applying with a brush, the weight ratio of the solvent should preferably be, for example, 10 wt% to 30 wt% when the entire decorative composition is taken as 100 wt%.

The viscosity of the decorative composition can be adjusted appropriately depending on the application method of the decorative composition and is not particularly limited. The viscosity of the decorative composition may be, for example, approximately 10 mPa·s to 500 mPa·s. The viscosity of the decorative composition can be adjusted appropriately by the amount of solvent or the addition of resin balsam, etc.

The decorative composition disclosed herein may additionally contain other components as appropriate, as long as the effects of the technology disclosed herein are not significantly impaired. Examples of additional components include organic binders, protective materials, surfactants, dispersants, thickeners, pH adjusters, preservatives, antifoaming agents, plasticizers, stabilizers, and antioxidants.

The decorative composition disclosed herein can be produced, for example, by mixing materials containing the desired metal elements in a predetermined ratio so as to contain at least a precious metal component and a matrix-forming component. As mentioned above, the form of the precious metal component and matrix-forming component contained in the decorative composition disclosed herein is not limited to metal resinates, but may also be complexes, polymers, or fine particles. When the precious metal component and matrix-forming component are in a form other than metal resinates, it is preferable to appropriately change the solvent and additional components described above depending on the form of the precious metal component and matrix-forming component. For example, when the precious metal component and matrix-forming component are contained in a form that is insoluble in a solvent, such as fine particles, it is preferable to select a solvent that can appropriately disperse the fine particles and to add a dispersant or other additional component.

3. Manufacturing Method of Ceramic Product Next, an example of a method for manufacturing the ceramic product disclosed herein will be described. Note that the ceramic product disclosed herein is not limited to those manufactured by the following manufacturing method.

(1) Preparation of Substrate When manufacturing the ceramic product according to this embodiment, first, a desired substrate is prepared. For example, the substrate can be prepared by molding and firing a substrate material in which a predetermined ceramic material is kneaded. Also, a substrate with a coating layer can be prepared by applying a glaze to the surface of the fired substrate and then firing it again. However, this process is not particularly limited as long as the substrate can be prepared. For example, a separately prepared substrate may be purchased and prepared.

(2) Formation of Silver Decorative Portion Next, in the production of a ceramic product according to this embodiment, a silver decorative portion is formed on the substrate (or coating layer). This silver decorative portion can be formed by applying (applying) the decorative composition described above to the surface of the substrate or coating layer, followed by firing at a predetermined temperature. A suitable example of the firing process in this step involves using the decorative composition disclosed herein for "overglaze painting," which involves decorating a substrate with a coating layer after a glaze has been applied. In overglaze painting, the decorative composition is applied to the glaze surface, followed by firing at a moderate temperature of approximately 700°C to 1000°C. The decorative composition disclosed herein can also be used for "underglaze painting," which involves decorating a bisque-fired substrate (ceramic substrate). In underglaze painting, the decorative composition is applied to the substrate, followed by firing at a high temperature of approximately 1200°C to 1400°C. Examples of methods for applying the decorative composition include brush painting, screen printing, and inkjet printing.

In this way, it is possible to realize ceramic products with silver decorative parts that are glossy, clear, and have good color development. It is also possible to realize decorative compositions that can suitably form such silver decorative parts. As mentioned above, "ceramic products" include pottery, porcelain, earthenware, stoneware, glass, etc., and specific products include, for example, tableware, decorative utensils, various tiles, sanitary ware, roofing tiles, bricks, clay pipes, and ceramic pipes. In particular, the technology disclosed herein makes it possible to suitably realize tableware with silver decorative parts that are glossy, clear, and have good color development.

<Test Example>
Test examples relating to the technology disclosed herein will be described below, but it is not intended that the technology disclosed herein be limited to such test examples.

1. Study of the structure of the silver decorative part In this test, ceramic products with silver decorative parts were produced and the characteristics of the silver decorative parts were evaluated. Specifically, glossiness (8° gloss value), color development (8° gloss value/lightness L ^* ), and field emission scanning electron microscope (FESEM) observations were performed. The structure of the silver decorative part with good color development and gloss was then studied.

(1) Preparation of Decorative Composition In this test, precious metal elements and matrix-forming elements were mixed to obtain the composition shown in Table 1. Each value in Table 1 represents the content (mol %) of each element when the total of the precious metal elements and matrix-forming elements contained in the decorative composition is taken as 100 mol %.
Each decorative composition was prepared in the same manner as described above. In this manner, decorative compositions of Examples 1 to 20 were prepared. The raw materials of the precious metal components and matrix-forming components used in these compositions are listed below.
Pt: Pt resinate (platinum resin sulfide balsam)
Rh: Rh resinate (rhodium resin sulfide balsam)
Au: Au resinate (gold resin sulfide balsam)
Si: Si resinate (silicon resin acid salt)
Bi: Bi resinate (bismuth resinate)
Al-1: Al resinate (aluminum resinate)
Al-2: Al ₂ O ₃ nanoparticle slurry (average particle size 50 nm)
Al-3: Aluminum chelate compound (ALCH)
Zr: Zr resinate (zirconium resinate)
Y: Y resinate (yttrium resinate)
Ca: Ca resinate (calcium resinate)

(2) Application of Decorative Composition and Firing A white porcelain plate (length: 15 mm, width: 15 mm) with a glaze applied to its surface was prepared as a substrate with a coating layer, and the decorative composition prepared above (any of Examples 1 to 20) was applied (coated) to the entire surface of one side of the white porcelain plate. The thickness of the silver decorative portion after firing was adjusted to 50 to 150 nm. To apply the decorative composition, a spin coater (Opticoat MS-A-150) manufactured by Mikasa Co., Ltd. was used, and the spinning conditions were set to 5000 rpm and 10 seconds. The white porcelain plate with the decorative composition applied was dried on a hot plate at 60°C for 1 hour and then fired at 800°C for 10 minutes. This resulted in the white porcelain plates (ceramic products) of Examples 1 to 20 with silver decorative portions formed on their surfaces.

(3) Gloss and Color Development Evaluation The 8° gloss value, L ^* value, a ^* value, and b ^* value of the white porcelain plate with the silver decorative portion formed thereon were measured using a spectrophotometer (CM-700d, manufactured by Konica Minolta Sensing Co., Ltd.) in accordance with JIS Z 8722:2009. The 8° gloss value was measured using the SCI method, and the L ^* value, a ^* value, and b ^* value were measured using the SCE method. In addition, the 8° gloss value/brightness L ^* was calculated from the 8° gloss value and lightness L ^* . Silver decorative portions with an 8° gloss value of 500 or more and an 8° gloss value/brightness L ^* ratio of 11 or more were evaluated as having good gloss and color development. The results are shown in Table 2.

(4) FESEM Observation FESEM observation was performed on the white porcelain flat plate with the silver decorative portion formed. First, each sample was fixed horizontally on a sample stage with the side coated with the decorative composition (i.e., the surface of the silver decorative portion) facing up, and then coated using an osmium plasma coater (manufactured by Japan Laser Electronics Co., Ltd.: OPC80N) to prepare a measurement sample with an osmium-coated surface. The discharge voltage for the osmium coating was 1.2 kV, the vacuum level was 6 to 8 Pa, and the coating time was 10 seconds. Next, five FESEM images of the surface of the silver decorative portion were obtained using a field emission scanning electron microscope (manufactured by Hitachi High-Technologies Corporation: SU8230). The acceleration voltage for obtaining the FESEM observation images was 10.0 kV, and the emission current was 10 ± 0.5 μA. The magnification of the field of view was adjusted to 2000 to 100,000 times so that the number of particles that could be counted in one field of view was 1,000 to 10,000. As an example, FESEM observation images of Examples 1 and 11 are shown in Figures 1 and 2.

Next, the five acquired FESEM images were binarized using the well-known image processing software Image J (ver. 1.53e) so that the precious metal components were colored black and other components (e.g., matrix-forming components) were colored white. As an example, the binarized images for Examples 1 and 11 are shown in Figures 3 and 4. The brightness threshold used to distinguish between the precious metal component regions and other component regions in the acquired FESEM images was determined using Image J's automatic settings. Areas above the brightness threshold were then designated as precious metal component regions, and areas below the brightness threshold were designated as other component regions, and binarization was performed. The area of the black portion of each of the five FESEM images relative to the total area of the FESEM image was calculated. The area ratio (%) of the precious metal components based on the FESEM observation was then calculated by averaging these values. The results are shown in Table 2.

Furthermore, the "Analyze particles" function of the well-known image processing software Image J (ver. 1.53e) was used to measure the individual area of the particles in the FESEM observation images obtained above for each example, and the cumulative 50% particle diameter (D ₅₀ ) in the number-based particle size distribution, the cumulative 90% particle diameter (D ₉₀ ) in the number-based particle size distribution, and the arithmetic mean diameter were calculated. The measurement conditions at this time were set to 0-infinity for both size and circularity. Then, a number-based particle size distribution was created in which the circle-equivalent diameters calculated for at least 1,000 particles were arranged in order of particle size, and the particle diameter corresponding to a cumulative frequency of 50 number% in the particle size distribution was defined as D ₅₀ , and the particle diameter corresponding to a cumulative frequency of 90 number% was defined as D ₉₀ . Furthermore, the average value of the circle-equivalent diameters for at least 1,000 particles was defined as the arithmetic mean diameter.

As shown in Table 2, Examples 3 to 5 and Examples 9 to 19 have 8° gloss values of 500 or more, and 8° gloss value/lightness L ^* of 11 or more. Therefore, the silver decorative portions of the ceramic products of Examples 3 to 5 and Examples 9 to 19 have excellent color development and luster. Furthermore, Examples 3 to 5 and Examples 9 to 19 have an area ratio of precious metal components of 37% or more based on FESEM observation. Furthermore, Examples 3 to 5 and Examples 9 to 19 have an area ratio of the precious metal components of 37% or more and a _D50 of 5 nm or more. Furthermore, Examples 3 to 5 and Examples 9 to 19 have an area ratio of the precious metal components of 37% or more and a _D90 of 20 nm or more. It can also be seen that in Examples 3 to 5 and Examples 9 to 19, the area ratio of the noble metal component is 37% or more and the arithmetic mean diameter is 35 nm or more.

As shown in Tables 1 and 2, Examples 3 to 5, which were fired using decorative compositions containing 50 mol% to 75 mol% of precious metal elements, had 8° gloss values of 500 or more and 8° gloss value/lightness L ^* of 11 or more. On the other hand, Examples 1 and 2, which were fired using decorative compositions containing 76 mol% or more of precious metal and no second element, and Examples 6 and 7, which were fired using decorative compositions with low precious metal contents, had 8° gloss values of less than 500 and 8° gloss value/lightness L ^* of less than 11. It is presumed that when a silver decorative part is formed by firing a decorative composition containing 76 mol% or more of precious metal, the color development is poor due to over-sintering of the precious metal particles. On the other hand, when a silver decorative part is formed by firing a decorative composition with a low precious metal content, it is presumed that the color development is poor because the portion derived from the precious metal element becomes thinner, allowing the color of the base to show through.

As shown in Tables 1 and 2, even when the content of the precious metal element was 76 mol% or more, the silver decorative parts of Examples 9 to 19, which were fired using decorative compositions containing 1.5 mol% or more of at least one element selected from the group consisting of Al, Zr, Ti, and rare earth elements as the second element, had an 8° gloss value of 500 or more and an 8° gloss value/lightness L ^* of 11 or more. On the other hand, Example 8, in which the content of the second element was 1.5 mol% or less, and Example 20, which did not contain the second element described above as a matrix-forming element, had an 8° gloss value of less than 500 and an 8° gloss value/lightness L ^* of less than 11. When the second element was not contained in an amount of 1.5 mol% or more, or when Ca was used as in Example 20, it is presumed that the effect of suppressing over-sintering of the precious metal particles as described above was insufficient, and therefore the effect of improving the gloss and color development of the silver decorative parts was not achieved.
Therefore, a decorative composition containing a precious metal element including at least Pt, a first element including at least one of Si and Bi as a matrix-forming element, and a second element including at least one selected from the group consisting of Al, Zr, Ti and rare earth elements, in which the content of the precious metal element is 76 mol% or more and 95 mol% or less and the content of the second element is 1.5 mol% or more, can form a silver decorative portion of a ceramic product with good color development and luster.

2. Study of the Type and Content of the Second Element Based on the above study, this test investigated the type and content of the second element that could improve the 8° gloss value and 8° gloss value/lightness L ^* in a fired body (silver decorative part) of a decorative composition containing at least a precious metal element and a matrix-forming element, with a precious metal content of 76 mol% or more. In this test, in addition to the decorative compositions (Examples 1 to 20) examined in the above test, six decorative compositions (Examples 21 to 26) with different compositions were prepared and evaluated for gloss (8° gloss value), color development (8° gloss value/lightness L ^* ), and insulating properties. In Examples 21 to 26, the precious metal element and the matrix-forming element were mixed to obtain the composition shown in Table 3. Each value in Table 3 represents the content (mol%) of each element when the total of the precious metal element and the matrix-forming element contained in the decorative composition is taken as 100 mol%.

(1) Preparation of Decorative Compositions Each decorative composition was prepared in the same manner as described above. In this manner, decorative compositions of Examples 21 to 26 were prepared. The raw materials for the precious metal components and matrix-forming components used here are listed below.
Pt: Pt resinate (platinum resin sulfide balsam)
Rh: Rh resinate (rhodium resin sulfide balsam)
Au: Au resinate (gold resin sulfide balsam)
Si: Si resinate (silicon resin acid salt)
Bi: Bi resinate (bismuth resinate)
Al-3: Aluminum chelate compound (ALCH)
Ti: Ti resinate (titanium resinate)
Y: Y resinate (yttrium resinate)
Sm: Sm resinate (samarium resinate)
Mg: Mg resinate (magnesium resinate)

(2) Application of Decorative Composition and Firing A white porcelain plate (length: 15 mm, width: 15 mm) with a glaze applied to its surface was prepared as a substrate with a coating layer, and the decorative composition prepared above (any of Examples 21 to 26) was applied (sprayed) to the entire surface of one side of the white porcelain plate. The thickness of the silver decorative portion after firing was adjusted to 50 to 150 nm. The decorative composition was applied in the same manner as described above. The white porcelain plate with the decorative composition applied was dried on a hot plate at 60°C for 1 hour and then fired at 800°C for 10 minutes. This resulted in the white porcelain plates (ceramic products) of Examples 21 to 26 with silver decorative portions formed on their surfaces.

(3) Evaluation of Gloss and Color Development The L ^{*, a*, b*, and 8° gloss values of the white porcelain flat plates (Examples 21-26) with the silver decorative portions formed thereon were measured using the spectrophotometer described above. The 8° gloss value was measured using the SCI method, while the L* , a * ,} and b ^* values were measured using the SCE method. The 8° gloss value/lightness L ^* was calculated from the 8° gloss value and lightness L ^* . Silver decorative portions with an 8° gloss value of 500 or greater and an 8° gloss value/lightness L ^* ratio of 11 or greater were evaluated as having good gloss and color development. The results are shown in Table 4. For comparison, Table 4 also lists the measurement results of Examples 1-20.

(4) Evaluation of Insulation The sheet resistance (Ω/□) of the white porcelain flat plates (Examples 1 to 26) on which the silver decorative portions were formed was measured. The sheet resistance was measured by the four-probe method using a resistivity meter (Loresta GP MCP-T610) manufactured by Mitsubishi Chemical Analytech Co., Ltd. A resistance of 1 x 10 ⁴ Ω/□ or higher was evaluated as having sufficient insulation. The results are shown in Table 4.

As shown in Table 4, Examples 3 to 5, 9 to 19, and 21 to 24 have an 8° gloss value of 500 or more, an 8° gloss value/lightness L ^* of 11 or more, and a sheet resistance of 1 x 10 ⁴ Ω/□ or more. Therefore, it can be seen that the silver decorative portions of the ceramic products of Examples 3 to 5, 9 to 19, and 21 to 24 have good color development and gloss, and further have sufficient insulation.

As shown in Tables 1, 3, and 4, even when the content of precious metal elements was 76 mol% or more, the silver decorative portions of the ceramic products of Examples 9 to 19 and Examples 21 to 25, which were produced by firing decorative compositions containing 1.5 mol% or more of at least one element selected from the group consisting of Al, Zr, Ti, and rare earth elements as the second element, had 8° gloss values of 500 or more and 8° gloss value/lightness L ^* of 11 or more. Furthermore, when the second element contained 10 mol% or more of Al, the silver decorative portions of the ceramic products of Examples 9 to 19 and Examples 21 to 24, which were produced by firing decorative compositions containing 2 mol% or more of a rare earth element as the second element, had sheet resistances of 1 x 10 ⁴ Ω/□ or more.
Therefore, a decorative composition containing at least a precious metal element including Pt, a first element including at least one of Si and Bi as a matrix forming element, and a second element including at least one selected from the group consisting of Al, Zr, Ti, and rare earth elements, in which the content of the precious metal element is 76 mol% to 95 mol% and the content of the second element is 1.5 mol% or more, can form a silver decorative part of a ceramic product with good color development and luster.Furthermore, when the decorative composition contains 10 mol% or more of Al as the second element, a decorative composition containing 2 mol% or more of a rare earth element as the second element can form a silver decorative part of a ceramic product with good color development and luster and sufficient insulation.

While specific examples of the technology disclosed herein have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above.

Claims (9)

A decorative composition used for silver decoration of a ceramic substrate,
Contains at least a noble metal element and a matrix-forming element,
the noble metal element includes at least Pt,
the matrix-forming elements include a first element and a second element;
The first element includes Si and Bi ,
The second element includes at least one element selected from the group consisting of Al, Zr, Ti, and rare earth elements,
Here, in the molar ratio where the total of the noble metal element and the matrix-forming element is 100 mol %,
The content of the noble metal element is 76 mol% or more and 95 mol% or less,
A decorative composition having a content of the second element of 1.5 mol % or more. 2. The decorative composition according to claim 1 , wherein the content of said second element is 1.5 mol % or more and 15 mol % or less when the total of said noble metal element and said matrix-forming element is taken as 100 mol %. In a molar ratio where the total of the noble metal element and the matrix-forming element is 100 mol %,
Composition of:
Pt 60 mol% to 95 mol%,
a total of 0 mol % to 20 mol % of Au, Rh, Pd, and Ag;
a total of Si and Bi of 1 mol% to 16 mol%;
Al 0 mol% to 13 mol%,
Zr 0 mol% to 7 mol%,
Ti 0 mol% to 7 mol%,
Rare earth elements 0 mol% to 7 mol%
(However, when Al is 10 mol % or more, the rare earth element is 2 mol % or more.)
The decorative composition according to claim 1 or 2 , wherein a ceramic substrate;
A ceramic product comprising: a silver decorative portion formed on the ceramic substrate, the silver decorative portion being a fired body of the decorative composition according to any one of claims 1 to 3;
The silver decorative portion contains a precious metal component,
The 8 ° gloss value of the silver decorative part when measured by the SCI method is 500 or more, and
The 8° gloss value is the lightness L of the silver decorative part when measured by the SCE method. ^* The value divided by (8° gloss value/lightness L ^* ) is 11 or more. 5. The ceramic product according to claim 4, wherein the area ratio of the noble metal component in the silver decorative portion is 37% or more based on observation with a field emission scanning electron microscope (FESEM). the precious metal component comprises precious metal particles;
The noble metal particles have a cumulative 50% particle diameter (D ₅₀ 6. The ceramic product according to claim 5, wherein the average particle size is 5 nm or more. the precious metal component comprises precious metal particles;
The noble metal particles have a cumulative 90% particle diameter (D ₉₀ 6. The ceramic product according to claim 5, wherein the average particle size is 20 nm or more. the precious metal component comprises precious metal particles;
The ceramic product according to claim 5 , wherein the noble metal particles have an arithmetic mean diameter of 35 nm or more. The sheet resistance of the silver decorative portion is 1×10 ⁴ The ceramic product according to claim 4, having a modulus of elasticity of Ω/□ or more.